This invention relates to electrodes for electric arc welding, particularly to construction of such electrodes.
In tungsten inert gas (TIG) arc welding, tungsten electrodes are used in a gas shield atmosphere. The electrodes are conventionally made of solid tungsten or related material. However, the use of these solid tungsten electrodes has resulted in serious tungsten wastage.
One source of tungsten wastage has been in shortening standard length electrodes. Tungsten electrodes are generally purchased in standard lengths of approximately 6 or 7 inches long to take advantage of economies of using longer length electrodes. However, such longer length electrodes do not fit torches with short back caps, which must be used where accessibility to the weld area is limited. This requires the user to break the standard length electrode into the length of approximately 2 inches to fit the torch. In so doing, the user commonly uses a readily available tool, such as pliers or a bench vise. In attempting to break off proper length of the electrode, the brittle electrode material can shatter into a number of unusable short pieces of less than an inch long or can split along its length, and split electrodes cannot be used since the split would cause unstable and erratic arc action.
Tungsten wastage also occurs in torches in which a standard length electrode can be employed, such as torches having a long back cap. With these torches the user is periodically required to provide a fresh point to the electrode if the electrode has been contaminated by touching the workpiece. Often, the user again uses pliers and similar tools to break away the contaminated section. While only about 1/2 inches of the electrode need be removed, the user in many cases invariably breaks away a piece of at least 1 inch resulting in unnecessary wastage. In addition, tenaciously adhering metal vapors are often deposited on the electrode periphery behind the point during welding. This contamination may require pieces of up to an inch or more in length to be broken off before an uncontaminated portion of the electrode is reached.
Tungsten wastage also results from the attachment of the electrode to the torch. When a standard length electrode is used, the loss of the usable tungsten electrode portion in the stub attached to the torch can be as much as 11/4 to 13/4 inches in length because of the chucking limitations of most conventional TIG torches.
Other problems of prior art tungsten electrodes arise when the electrode must be pointed. After breaking off a contaminated section, the user must grind a new point on the electrode in the case of DCSP welding (or a squared end in the case of AC welding). Also new tungsten electrodes which are commonly shipped with a squared end for AC welding require pointing for DCSP welding. This pointing or repointing is often done on a general purpose grinding wheel, the surface of which has been contaminated by grinding other objects such as tool bits. The contaminants from the grinding wheel can be transferred to the pointed surface on the tungsten electrode, and these contaminants on the electrodes can cause electrode spitting and erratic arc action. Spitting results in tungsten inclusions in the weld which provide unacceptable results since these inclusions adversely affect weld joint strength.
It has been found that an exact angle must be provided on the tungsten electrode tip in DCSP welding for proper and consistent weld penetration. Yet, it is impossible for the operator without accurate measuring to achieve the proper and required point angle while grinding.
The electrodes of the present invention, however, reduce the difficulties indicated above and afford other features and advantages heretofore not obtainable.